A noivel technique for chemical investigations of metabolic processes will be developed and exploited. We will use fluorine as a stable isotope, heteroatomic label to detect and identify metabolic intermediates present in low concentrations. The key analytical technique for detection of carbon-bound fluorine will employ an inductively coupled plasma source for emission spectroscopy interfaced to a gas chromatograph. The tagging and metabolic blocking capabilities of fluorinated analogues of normal biological substrates will be explored by studying the biosynthesis of cyclonerodiol from farnesyl pyrophosphate in the fungus Gibberella fujikuroi. These capabilities will be used to investigate the novel transformation of farnesyl pyrophosphate in to cantharidin in Epicauta and Lytta blishter beetle species. We will focus on the identification of intermediates in this pathway to reveal the sequence of bond making and breaking events, as well as the specific chemical reactions likely to be involved. The fluorolabel technique will provide a new tool for detecting intermediates in low concentrations to provide insight into the molecular events in metabolic processes. Identification of intermediates in the biosynthesis of cantharidin will reveal details about a novel biological approach to the assembly of natural products from simple precursors. Detection of other fates of fluorofarnesols will provide initial evidence regarding insect metabolism of farnesyl pyrophosphate, a hormonal precursor, about which little is known.